Selective relay



Nov. 1, 1949.

G. EANNARINO 2,486,394

SELECTIVE RELAY Filed Feb. 25, 1946 GEORGE- EAN/V/l Rl/VO Patented Nov.1, 1949 SELECTIVE RELAY George Eannarino, North Arlington, N. 1.,assignor to Federal Telephone and Radio Corporation, New York, N. Y., acorporation of Delaware Application February 25, 1946, Serial No.650,052

6 Claims. (Cl. 200-90) This invention relates to a relay suitable foruse in selective signalling systems or more particularly to a selectivesignalling device for mobile equipment using a vibrating reed in themobile receiver.

It is therefore an object of the invention to provide a relay having avibrating reed which has a natural frequency of vibration and which isso constructed that it is responsive to signals having a frequencycorresponding to the natural frequency of the reed. A further objectresides in providing a relay with a fixed magnet having a vibrationamplifying effect to permit the attainment of large vibration amplitudewith very low energ zing power. Another object resides in theinterchangeability of the vibrating reed to difierent natural resonantfrequency to thereby cover a considerable range of resonant frequenciesby changing the metal thickness of the reed.

Further objects will be apparent from the fol lowing description whenconsidered in connection with the accompanying drawing.

The drawing shows a preferred form of the relay as an example in which:

Figure 1 is a longitudinal sectional view of the relay, certain elementsbeing shown in elevation,

Fig. 2 is an end elevation of the left end of the relay of Fig. 1, and IFig. 3 is an end elevation of the right end of the relay of Fig. 1.

In both Figs. 1 and 2, one of the solder tenninals of the relay has beenomitted for simplicity of showing.

Referring to Fig. l of the drawing, the relay is formed of a U-shapedframe or housing I preferably consisting of a strip of non-magneticmetal, such as brass, of uniform thickness and width and having aninwardly bent end portion la, a straight side portion I b, a yokeportion I c, a sec-- ond straight side portion Id and a second inwardlybent portion Ie. The two side portions Ib and Id are each'provided witha longitudinal slot near the center thereof to receive a spool 2carrying the relay winding or coil 3. The spool 2 is provided with atubular core 2a of square section, Fig. 2, and a vibrating reed 4' ofthe relay is mounted to extend through the center of the square tube 2a.

The reed 4 is formed of two magnetic strips 4a and 4b preferably of softiron and preferably riveted on opposite sides of a strip of spring brassor bronze or steel 40 which forms a hinge element.

The spring 40 is securely clamped between two blocks 5a and 5b ofsuitable insulating material, which are mounted between the two sidearms Ib and Id -of the frame I. The two blocks 5a. and 5b are clampedtogether by means of a screw 9 which passes through aligned holes formedin the ends of the frame sides Ib and Id and through holes formed in theblocks 5a and 5b and through a hole formed in the spring member 40. Aclamping nut I0 is threaded on the other end of the screw 9, with aspring washer II interposed. An insulating sleeve 8 surrounds the screw9 and passes through the hole formed in the spring member 4c and islocated in counterbores formed in the blocks 5a and 5b. This sleeve 8serves to insulate the reed from the screw 9. The spring member 40extends beyond the blocks 5a and 5b, and a terminal element 4d issecured to the end of the spring member 4c, Fig. 1.

A permanent magnet 6, preferably in the form of a round bar, is providedinside of the yoke portion to of the frame and is positioned between twopole pieces I and 1'. These pole pieces I and l are composed of magneticmaterial and preferably of soft iron and are formed in an L-shapedsection. The ends of the magnet 6 are preferably received in circularsockets formed in the horizontal portions of pole pieces I and l, andthe pole pieces and the magnet are locked within the frame by means ofrelatively thin and narrow extensions la and 7a formed on the polepieces and extending through slots formed in the relay frame 5 near theends of the yoke portion Ic. Locking of the parts together is secured bybending over the ends of the extensions as shown in Fig. i. The poletips lb and lb of the pole pieces 5 and 'l' are spaced apart, and thefree ends of the reed strips 4a and 4b extend into the space betweenthese pole tips. The reed strip 4b is provided with a contact member 24which is arranged to engage the end of a threaded contact stud l4mounted in a hole formed in the frame side portion If). This stud isadjustable to and from the reed armature by threaded engagement with abushing I2 which is insulated from the frame of the relay by means ofinsulating washers I 5 and an insulating bushing I6. The contact stud I4is also provided with a pair of nuts I8 and I9 and a washer iii.

The terminals of the coil 3 are connected to a pair of terminals 23a and23b mounted on the outer face of insulating blocks 5a and 5brespectively by means of hollow eyelets 22. The signal currents foroperating the relay are supplied to these terminals 23a and 23b. Thecircuit to be controlled by the relay would for example include a sourceof low voltage and would be connected to terminal 4d on the reed 4 andto the contact stud I4. When the coil 3 is energized by alternatingcurrent, the free end of the reed strips 4a and 4b will be magnetizedwith one polarity during one alternation and will be attracted to thepole piece of opposite polarity, while during the next alternation thepolarity of the reed strips will be reversed and they willbe attractedto the opposite pole piece. Thus, the free end of the reed tends tovibrate in synchronism with the alternating current supplied to coil 3.When the frequency of the current corresponds to the natural frequencyof the reed, the amplitude of vibration of the reed will be sufficientto cause the reed piece 4b to remain in contact with the inner end ofcontact stud H for a substantial period of time during each cycle ofvibration, and thus the relay responds selectively to a current of apredetermined frequency. By changing the natural frequency of the reed.as by substituting for reed strips 4a and 4b similar strips of greaterthickness, the reed may be made sensitive to a different frequency.

An escutcheon pin 20 for-med of non-magnetic material is inserted in theface of pole piece I to prevent the reed strip 4a from coming in directcontact with the face of pole piece I.

It is thus clear from the foregoing that when an alternating currentflows in the coil 3, the vibrating reed becomes magnetized in alternatedirections. If on the positive half of the A. 0. cycle the free end ofthe reed becomes a north magnetic pole, it will be repelled by the northpole of the magnet and attracted to the south pole. For the negativepart of the A. C. cycle the free end of the reed will become a southpole which is now repulsed by the south pole of the magnet and attractedby the north pole. If the frequency of magnetization of the reed by thecoil is the same as the natural vibrating frequency of the reed, thelatter will vibrate in the air gap and the vibration amplitude willincrease until the reed contact point strikes the fixed contact. Thevibration amplitude will then be the total of the distance between thecontact and vibrating reed.

Due to the vibration amplifying effect of the fixed magnet the unit iscapable of attaining large vibration amplitude with very low energizingpower. This is particularly important in battery energized systemswherein the relay is controlled by a vacuum tube because high systemssensitivity can be obtained with relatively few tubes.

It is possible to change the natural resonant frequency of the vibratingreed to cover a considerable range of resonant frequencies by changingthe metal thickness of the reed, by changing other dimensions of thereed, the weight distribution of the reed, the stiffness of the hingespring or by other well known means. Also, although I have shown thereed as comprising two strips 4a and 4b, a reed consisting of a singlestrip may be employed.

By mounting the reed co-axially with the energizing coil as shown, a.relay whichis simpler to manufacture and which is more compact andlighter in weight than other types of selective relays can be obtained.

While I have shown a particular embodiment of my invention for thepurposes of illustration and description, changes and modificationstherein will be apparent to those skilled in the art without departingfrom the scope of my invention.

I claim as my invention:

1. A relay particularly for selective signalling comprising a frame, aresilient member insulatingly clamped at one end to said frame, a reedincluding two parallel strips of magnetizable material clamped at oneend thereof to opposite sides of said member, the other end of said reedbeing free to vibrate, a permanent magnet secured in said frame adjacentsaid other end of said reed and having a pair of spaced pole piecesbetween which said reed vibrates, means for preventing said reed fromcoming into direct contact with the pole pieces of said magnet, and acoil secured in said frame positioned between said member and saidmeans, said coil surrounding said reed and vibrating same in resonancewith its natural period.

2. A relay particularly for selective signalling as claimed in claim 1,wherein said means for preventing said reed from coming into directcontact with the pole pieces of said magnet comprise a non-magnetizablematerial attached to the face of the first of said pole pieces of saidmagnet and with which material one of the strips of said reedcooperates, a first contact attached to the other of the strips of saidreed, a second contact insulatingly attached to said frame adapted toengage said first contact when said reed is energized at its resonantfrequency and adjusted to prevent said reed from striking the second ofsaid pole pieces.

3. A relay particularly for selective signalling as claimed in claim 2,wherein said contacts are in contact for a substantial period of timeduring each cycle of vibration whereby the relay is responsiveselectively to a current of a predetermined frequency.

4. A relay particularly for selective signalling as claimed in claim 1,wherein a tubular core is provided between said coil and said reed, saidreed passing through said core with minimum clearance.

5. A relay particularly for selective signalling as claimed in claim 1,wherein said reed is of a magnetizable material having high permeabilityand low retentivity.

6. A relay particularly for selective signalling comprising a U-shapedframe, a pair of insulating blocks clamped between the open ends of saidframe, a permanent magnet in the closed end of said frame, with its endsfacing the sides of said frame, a pair of L-shaped pole pieces withinsaid frame, the first portions of each of said pieces being disposedbetween the respective ends of said magnet and the sides of said frame,said pieces being provided with an integral extension lug at the ends ofthe first portions thereof, each lug protruding through an aperture inthe closed end of said frame and being .bent to secure said pieceswithin said frame, said pole pieces forming a gap between the ends ofthe second portions thereof, said second portions retaining said magnetagainst the closed end of said frame, a vibrating reed clamped betweensaid blocks extending toward the closed end of said frame, said reedvibrating in the direction of both sides of said frame, within the gapformed by said pole pieces and a coil secured in said frame positionedbetween said blocks and said.

pole pieces, said coil surrounding said reed and vibrating same inresonance withits natural I period. r

' GEORGE EANNARINO.

REFERENCES crrnn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

